The aims of this study were to 1) compare two methods of determining interstitial glycerol concentration in subcutaneous adipose tissue (AT) and 2) determine whether there are regional differences in interstitial glycerol concentration in subcutaneous AT of non-obese, pre-menopausal women. Micro-dialysis probes were inserted under local anesthesia into the abdominal (2 probes) and femoral (1 probe) subcutaneous AT in each subject (n=5) and perfused with a Ringer solution containing 2.5 mM glucose and glycerol in concentrations ranging from 0-900 (M. It can be concluded that the interstitial glycerol concentration in the femoral AT of non-obese, pre-menopausal females is ~240 (M and is higher than in abdominal AT . Furthermore, the use of a stable isotope of glycerol as an internal reference is suitable for determining interstitial glycerol concentrations in subcutaneous adipose tissue in humans at rest.